A Groundbreaking Revelation at the AGU Annual Meeting

In a stunning presentation at the American Geophysical Union's annual meeting in 2018, researchers unveiled an astonishing discovery: a vast cache of life thriving beneath our feet, far exceeding their expectations.

A Gigantic Microbial Population

Approximately 70% of Earth’s microbial population calls the underground home, boasting an astonishing carbon composition of 15 to 23 billion tonnes—dwarfing our planet's human carbon footprint.

The ‘Subterranean Galapagos’

While scientists have only just begun exploring these hidden microorganisms, initial findings hint at a genetic diversity that rivals or even surpasses that of surface life. This captivating ecosystem has aptly been dubbed the "subterranean Galapagos," though you won’t find giant tortoises here. Instead, it’s a world dominated by bacteria, archaea, and surprising eukarya, including an unidentified nematode discovered deep within a South African gold mine at over 1.4 kilometers (0.8 miles) down.

Expanding Horizons

Karen Lloyd, an Associate Professor of microbiology at the University of Tennessee and a key contributor to the study, noted a significant shift in understanding this underground realm. "Ten years ago, we sampled only a handful of sites we thought could harbor life. Now, with ultra-deep sampling, we've discovered that these microorganisms appear almost everywhere, although we’ve only explored a minuscule part of the deep biosphere.”

An Unfathomable Volume of Life

The research team synthesized dozens of previous studies, analyzing samples extracted from depths of 2.5 to 5 kilometers (1.55 to 3.1 miles) below the surface, both from continental and oceanic environments. Notably, they found the deep subsurface biosphere is nearly twice the volume of all Earth’s oceans, prompting awe and excitement.

Surviving the Harsh Conditions

This extraordinary ecosystem exists under extreme conditions: intense heat, crushing pressure, total darkness, and minimal nutrients. Yet, it may illuminate mysteries surrounding the limits of life on our planet—and possibly beyond.

A Call for Further Exploration

Rick Colwell, a microbial ecologist at Oregon State University, emphasized the depth of knowledge yet to be uncovered: "While our studies have unveiled new insights into these deep biosphere microbes, they have also highlighted how much remains a mystery. The interactions between subsurface and surface life are still largely unknown, leaving us in awe of the resilient metabolisms that allow life to thrive in such harsh conditions.”